How to Predict the Efficacy of Free-Product DNAPL Pool Extraction Using 3D High-Precision Numerical Simulations: An Interdisciplinary Test Study in South-Western Sicily (Italy)
, Federica Lo Medico 2,*, Pietro Rizzo 1, Maurizio Gasparo Morticelli 2, Riccardo Pinardi 1, Edoardo Rotigliano 2 and Fulvio Celico 1
Round 1
Reviewer 1 Report
hydrology-2434979: How to predict the efficacy of free-product DNAPL pools extraction using 3D high-precision numerical simulations: an interdisciplinary test study in South-Western Sicily (Italy).
This manuscript employed a numerical model to simulate the free product DNAPL extraction at a field site in Sicily, which is contaminated tetrachloroethylene and trichloromethane. Certainly, the research topic is very interesting because many aquifers throughout the world are contaminated with DNAPLs. The manuscript is organized and written relatively well. The numerical modeling is somewhat sketchy. The figures are clear and the captions are informative. The results are useful. Consequently, this reviewer recommends publication of this manuscript in Hydrology after a relatively minor revision. The following is a short list of suggestions that may improve this manuscript prior its publication:
(1) The introduction should be expanded to cover previous pertinent work on NAPL free product extraction as well as dissolution in porous media.
(2) Lines 40-43: This paragraph should be expanded. It will be beneficial to the readers to know that not only numerical models are available in the literature, but numerous analytical models for single component NAPL (Transport in Porous Media, 16(2), 125–145, 1994; Water Resources Research, 31(4), 1137–1145, 1995) and multi-component (Journal of Hazardous Materials, B128, 218-226, 2006) dissolution in porous media have been published.
(3) The field site is contaminated with both PCE and TCM. Does the numerical model used can differentiate between a single component and multicomponent DNAPLs?
(4) The limitations of the numerical model used should be clearly presented in the revised manuscript.
(5) It is not clear how the progress of the natural attenuation process was monitored at the field site.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The main objective of this paper is using 3D high-precision numerical simulations to find the way for efficaciously removing DNAPL pools from aquifer systems. The numerical model simulates the free product DNAPL extraction in a synclinal aquifer type by means of a purpose-designed pumping well. Numerical methods are combined with biomolecular studies to analyze for the presence of native microorganisms that may be associated with biodegradation of chlorinated solvents. Coupling the numerical simulations to the bacterial community characterization, the authors predict that the PCE recovery through a pumping well will be almost complete, with the remaining PCE relying on native colonies for natural decay. In addition, the structure is clear, and its analyses and discussions in this paper are reasonable and logical. In my opinion, this manuscript has the potential to be published in “Journal of Hydrology” after revision. For further improvement, I would like to give some specific suggestions:
1. In lines 54-55, the statement “See, for example, recent results in transport modeling in a porous medium”. Please revise the introduction to avoid overly colloquial language.
2. In lines 64-70, please check the expression “Several validation tests were performed in [23,24,28,29] to verify the accuracy of the HRSC method and the CactusHydro code. CactusHydro is based on the Cactus computational toolkit [30–32], an open-source software framework for developing high-performance parallel computing (HPC) simulation codes, and the data are evolved on a cartesian mesh using Carpet [33,34]. Several validation tests were performed to verify the accuracy of the HRSC method and the CactusHydro code”. The first and last sentences are almost identical, making the text wordy. Please be concise in the text.
3. Figure 4 is too small to be seen. Please replace the picture to better illustrate the hydrogeology of the study area.
4. In lines 367-369, the statement “The aquifer medium is composed of an unsaturated dry zone (air), the one depicted in white in Figure 7, and a saturated one, the one depicted in blue, separated by a groundwater table surface with a hydraulic gradient of 7.1% towards SE”. Aquifers are composed of saturated and unsaturated aquifers. The air-filled unsaturated dry zone is only one part of the unsaturated aquifer. As mentioned earlier, the white area is an unsaturated aquifer. Please modify the text to make the description consistent.
5. Figures 7 and 9 are not very clear and do not show the green color representing the bottom of the aquifer and the atmosphere.
6. In Figure 8, the white cubic indicates the position of the well and the absence of contaminant. In lines 366-367, the authors stated that the DNAPL is positioned at (x, y, z)=(0,0,185.0)m and the extraction pumping is situated at (x, y, z)=(2,0,185.0)m. However, at t=0 s (see Figure 8 (a)), the white cubic positioned at (x, y, z)=(0,0,185.0)m is inconsistent with the description.
7. In lines 521, the word ”complete” should be in the passive voice.
The main objective of this paper is using 3D high-precision numerical simulations to find the way for efficaciously removing DNAPL pools from aquifer systems. The numerical model simulates the free product DNAPL extraction in a synclinal aquifer type by means of a purpose-designed pumping well. Numerical methods are combined with biomolecular studies to analyze for the presence of native microorganisms that may be associated with biodegradation of chlorinated solvents. Coupling the numerical simulations to the bacterial community characterization, the authors predict that the PCE recovery through a pumping well will be almost complete, with the remaining PCE relying on native colonies for natural decay. In addition, the structure is clear, and its analyses and discussions in this paper are reasonable and logical. In my opinion, this manuscript has the potential to be published in “Journal of Hydrology” after revision. For further improvement, I would like to give some specific suggestions:
1. In lines 54-55, the statement “See, for example, recent results in transport modeling in a porous medium”. Please revise the introduction to avoid overly colloquial language.
2. In lines 64-70, please check the expression “Several validation tests were performed in [23,24,28,29] to verify the accuracy of the HRSC method and the CactusHydro code. CactusHydro is based on the Cactus computational toolkit [30–32], an open-source software framework for developing high-performance parallel computing (HPC) simulation codes, and the data are evolved on a cartesian mesh using Carpet [33,34]. Several validation tests were performed to verify the accuracy of the HRSC method and the CactusHydro code”. The first and last sentences are almost identical, making the text wordy. Please be concise in the text.
3. Figure 4 is too small to be seen. Please replace the picture to better illustrate the hydrogeology of the study area.
4. In lines 367-369, the statement “The aquifer medium is composed of an unsaturated dry zone (air), the one depicted in white in Figure 7, and a saturated one, the one depicted in blue, separated by a groundwater table surface with a hydraulic gradient of 7.1% towards SE”. Aquifers are composed of saturated and unsaturated aquifers. The air-filled unsaturated dry zone is only one part of the unsaturated aquifer. As mentioned earlier, the white area is an unsaturated aquifer. Please modify the text to make the description consistent.
5. Figures 7 and 9 are not very clear and do not show the green color representing the bottom of the aquifer and the atmosphere.
6. In Figure 8, the white cubic indicates the position of the well and the absence of contaminant. In lines 366-367, the authors stated that the DNAPL is positioned at (x, y, z)=(0,0,185.0)m and the extraction pumping is situated at (x, y, z)=(2,0,185.0)m. However, at t=0 s (see Figure 8 (a)), the white cubic positioned at (x, y, z)=(0,0,185.0)m is inconsistent with the description.
7. In lines 521, the word ”complete” should be in the passive voice.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
